A semiconductor manufacturing process includes a step that supplies a treatment liquid onto a substrate to perform a liquid treatment to a substrate. Such a liquid treatment step is performed by ejecting from a nozzle the treatment liquid that has been fed from a treatment liquid tank through a supply passage. A filter unit is provided in the treatment liquid supply passage to remove foreign matters included in the treatment liquid in the treatment liquid tank or foreign matters originated from piping and supply devices.
If a treatment starts immediately after a new filter unit is installed in the piping at the starting-up or maintenance of the apparatus, the filtration performance of the filter unit (i.e., the cleanliness of a liquid flowing out of a filter) is not stable, and thus a treatment cannot be performed normally. Thus, after installation of the filter unit, a pretreatment, such as a repetitive dummy dispensing operation or a long time circulation of the solvent, is performed until the filtration performance of the filter unit becomes stable. Even after stating of the treatment using the new filter unit, the filtration performance of the filter unit deteriorates so that an operation such as the dummy dispensing is again needed.
However, such an operation increases the solvent consumption and prolongs the standby time before the liquid treatment of substrates, resulting in productivity decline. The inventors have found through their research that elution of resins from the filter part of the filter unit, caused by the solvent contained in the treatment liquid, is one of reasons for instability in filtration performance of the filter unit. It has been found through the inventors' research that foreign matters derived from the eluted substance invite defects on substrates. Under the recent circumstances where the allowable level of defects caused by foreign matters becomes severer because of miniaturization of patterns, the eluted substance from the filter part is not a negligible problem.
In addition, when a new resist liquid supply apparatus is installed or when the type of the resist liquid used in the resist liquid supply apparatus is changed, cleaning of the inside of the resist liquid supply passage is recommended. To this end, the piping is filled with deionized water and is left for a predetermined period of time. This cleaning process requires a long period of time and a large amount of cleaning liquid consumption. In addition, since circuit patterns becomes more complicated, it is required to eliminate causes of lowering the throughput, by removing organic matters adhering to the liquid contacting parts of the piping and the supply devices.
Patent Document 1 describes a method of lowering absorption of foreign matters to a filter part in a substrate processing apparatus by changing the temperature of the filter part. The problem to be solved by the method differs from that of the technique disclosed below.
Patent Document: JP2013-030690A